Vanessa Trump, the wife of Donald Trump Jr., was taken to a hospital Monday after opening a letter addressed to him that contained an unidentified, white powdery substance.
Preliminary investigation indicated the substance was not dangerous, the New York Police Department said.
The Fire Department said it responded to a call for help at an apartment building on East 54th Street in Manhattan at 10:03 a.m. Vanessa Trump, 40, had called 911 and said she was coughing and felt nauseated, the Associated Press reported, citing police.
Firefighters secured the scene, decontaminated it, and took three patients to New York-Presbyterian/Weill Cornell Medical Center, department spokeswoman Sophia Kim said.
The Fire Department did not identify the three people or provide reports on their conditions.
"The Secret Service and our law enforcement partners in New York City are investigating a suspicious package addressed to one of our protectees received today in New York, New York," special agent Jeffrey Adams said in a statement.
Donald Trump Jr., 40, is President Trump's eldest child, whom he had with his first wife, Ivana Trump.
3:15 p.m.: This article has been updated with the Secret Service participating in investigation.